This invention relates generally to seals for analytical instruments and particularly to a method and apparatus for preventing atmospheric gases from contaminating glow discharge spectral analyses.
Surface analysis or depth profiling of a conductive or non-conductive sample on a glow discharge spectroscope is finding wide acceptance. This is due in substantial part on the Grimm lamp design used on such instruments which provides convenient and rapid sample substitution. This is accomplished by simply placing the sample over the opening to the glow discharge lamp. The opening has an outer concentric O-ring which allows a vacuum seal to be substantially formed between the face of the Grimm lamp and the sample surface. However, because the sample surface is not always perfectly smooth, the vacuum used to retain the sample against the opening also draws atmospheric gases into the lamp. The presence of these gases can substantially alter the results of an analysis. To date, no suitable method has been proposed to prevent the Grimm lamp from aspirating atmospheric gases past the sample.